This invention relates to a construction for mounting an electronic component on a flexible substrate.
Conventionally, soldering or cold soldering techniques have been used, for allowing electrode portions of an electronic component of the chip type to be connected to a circuit pattern which has been formed by etching a copper foil disposed on a flexible substrate. Specifically, soldering cream is printed on a flexible substrate. Then, an electronic component of the chip type is placed on the soldering cream by means of an automatic mounting machine. Subsequently, the flexible substrate is directed into a heating furnace so as to cause the electronic component to be soldered on the flexible substrate.
It is noted that, since the flexible substrate tends to be easily deflected, sufficient connection strength is not obtained when the connection is performed by merely using a soldering operation. Thus, a U. V. curable adhesive is applied on the electronic component so as to encapsulate the electronic component. The thus encapsulated electronic component is directed into a U. V. irradiation furnace so as to be cured therein for the purpose of reinforcement.
When the circuit pattern is formed by printing silver paste on the flexible substrate, a problem regarding adhesive properties is caused, in contrast to the circuit pattern formed by etching a copper foil. Thus, a conductive adhesive of a hot melt type is conventionally used in place of a solder. It is also necessary to use a conductive adhesive, when a film having a low heat-resistive temperature (for example, polyethylene terephthalate (PET) film) is used as a flexible substrate.
In this case, a conductive adhesive is printed on the flexible substrate and then dried. An electronic component is placed on the conductive adhesive by means of an automatic mounting machine. Thereafter, the flexible substrate and the electronic component are heated and compressed together, so as to cause the conductive adhesive to melt, whereby the flexible substrate and the electronic component are connected together.
It is also noted that, in this case, not sufficient connection strength between the flexible substrate and the electronic component is obtained. Thus, a U. V. curable adhesive is applied on the electronic component so as to encapsulate it.
In any of the connection methods mentioned above, and when a large number of electronic components are to be mounted on a flexible substrate, the flexible substrate having mounted thereon the electronic components may be directed into a heating furnace or U. V. irradiation furnace, so as to cause the electronic components to be efficiently connected at one time.
It is noted, however, that, when a small number of electronic components are to be mounted on a flexible substrate, production efficiency is reduced. This is because that, even when a small number of electronic components are to be mounted on a flexible substrate, it is necessary for the electronic components to be mounted on the flexible substrate and directed into a heating furnace so as to cause the electronic components to be connected to the flexible substrate. Furthermore, it is necessary for the electronic components to be applied with a U. V. curable adhesive and directed into a U. V. irradiation furnace.
Installation of a heating furnace or a U. V. irradiation furnace also increases the cost of equipment.
In order to solve the above-mentioned problems, it is contemplated for individual electronic components to be mounted one by one on a flexible substrate, without using a heating furnace or the like. It is noted, however, that such a construction has not been proposed heretofore which facilitates simple and easy mounting of electronic components on a flexible substrate.